Catalyst system for the polymerization of olefins

ABSTRACT

An organometallic compound obtainable by contacting a compound having the following formula (I), wherein: R a  is a hydrocarbon radical; R b , R c  and R d , are hydrogen atoms, halogen atoms, or hydrocarbon radicals; with a Lewis acid of formula (11) MtR 1   3  (II) wherein Mt is a metal belonging to Group 13 of the Periodic Table of the Elements; R 1  are selected from the group consisting of halogen atoms, halogenated C 6 -C 20  aryl and halogenated C 7 -C 20  alkylaryl groups.

The present invention relates to organometallic compounds, to catalystsystems for the polymerization of olefins comprising such organometalliccompounds and to a process for the polymerization of olefins carried outin the presence of the above catalyst system.

Homogeneous catalytic systems based on metallocene complexes are knownto be active in the polymerization of olefins; said complexes must beactivated by means of suitable cocatalytic compounds.

The first generation of cocatalysts developed for homogeneousmetallocene olefin polymerization consisted of alkyl aluminum chlorides(AlR₂Cl), wherein substituents R are preferably methyl or ethyl; thesecocatalysts exhibit low ethylene polymerization activity levels andnegligible propylene polymerization activity.

The second generation of cocatalysts comprised the class ofalkylalumoxanes, commonly obtained by reacting trialkyl aluminumcompound and water in a molar ratio of 1:1 to 100:1; these alumoxanesare oligomeric linear and/or cyclic compounds represented by theformulae:

for linear oligomeric alumoxanes, and

for cyclic oligomeric alumoxanes, wherein the substituents R are usuallymethyl, ethyl or isobutyl groups, n ranges from 0 to 40, and m rangesfrom 3 to 40. Methylalumoxane (MAO) is the most widely used cocatalyst.

Nevertheless alkylalumoxanes, and in particular methylalumoxane, thoughvery active in metallocene-based catalyst systems, exhibit severalinherent problems in use, such as the need for highalumoxane/metallocene molar ratios to produce satisfactory catalyticactivities, their high reactivity toward impurities (moisture, alcoholsetc.) and their easy flammability. Moreover, it has not been possible toisolate characterizable metallocene active species using MAO.Accordingly, some of the developments in this area involved a search foralternative cocatalysts.

B(C₆F₅)₄ ⁻ types of non-coordinating anions have been developed ascocatalysts for metallocene-based systems. More specifically, theseactivators are ion-exchange compounds comprising a trialkyl ordialkylammonium cation, which will irreversibly react with ametallocene, and a fluorinated arylborate anion, capable of stabilizingthe metallocene cation complex and sufficiently labile to permitdisplacement by ethylene during polymerization (see for instance WO91/02012). In particular, they have the advantage of being used in a 1:1catalyst-cocatalyst ratio. Therefore, it is usually not necessary toremove the small amount of boron from the final polymer, unlike thealuminum-based cocatalysts mentioned above. As preferred activators aretri(n-butyl)ammonium tetrakis(pentafluorophenyl)boron andN,N-dimethylanilinium tetrakis(pentafluorophenyl)boron.

These cocatalysts exhibit high activities but, from a synthetic point ofview, the industrial production of these cocatalysts is quite expensive.

Finally, these B(C₆F₅)₄ ⁻ anions are generally used in the form of thecorresponding ammonium salts, thus leading to the release of aminicby-products in consequence of the metallocene activation. In additionthey have low solubility in polymerization solvents The fourthgeneration of cocatalysts is B(C₆F₅)₃. The anion MeB(C₆F₅)₃ ⁻ formedafter Me⁻ abstraction from the metallocene dimethyl complex is weaklycoordinated to the electrondeficient metal center, thus resulting in adecrease of the catalytic activity and in addition the catalyst systemis not stable.

An alternative route for using B(C₆F₅)₃ has been proposed by B. Temme inJournal of Organometallic Chemistry, 488 (1995), 177-182.Biscyclopentadienyl-methyl-pyrrolidyl zirconocene has been treated withB(C₆F₅)₃ with the formation of the pyrrolydyl borate and the metallocenecation. In this paper it is reported that the obtained salt iscatalytically active and polymerizes ethylene even if with a moderateactivity.

WO 99/64476 describes a process for the preparation of polyolefins byusing a catalyst system comprising a metallocene compound, a Lewisacid-base complex and a tri-n-alkylaluminum compound. As described atpage 4 and illustrated in the figures, the function of the Lewis base isto inhibit the reaction between the metallocene compounds and the Lewisacid. Only upon addition of the tri-n-alkylaluminum compound thecatalyst system becomes active. This catalyst system does not solvecompletely the problems of the use B(C₆F₅)₃, for the reason that theanion that is weakly coordinated to the electrondeficient metal centeris always of the type MeB(C₆F₅)₃ ⁻ and therefore the active catalystsystem is not stable for a long time.

The recently published WO 01/62764 describes a new class of cocatalystsobtainable by contacting a N—H pyrrole derivative with a Lewis acid. Thecatalyst system comprising these cocatalyts and a metallocene compoundcan be isolated and identified.

Thus there is still the need to find a new cocatalyst which reduces theuse of excess of cocatalyst with respect to alkylaluminoxanes, does notlead to the release of undesired by-products after the metalloceneactivation, and provides stable catalytic compositions.

The present invention concerns an organometallic compound obtainable bycontacting:

-   -   a) a compound having the following formula (I):        wherein:

R^(a) is a linear or branched, saturated or unsaturated, C₁-C₁₀ alkyl,C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl group, optionallycontaining O, S, N, P, Si or halogen atoms; or R^(a) can join R⁴ to forma C₄-C₇ ring; preferably R^(a) is a C₁-C₁₀ alkyl, or C₆-C₂₀ aryl group;more preferably R^(a) is methyl, ethyl, propyl, phenyl or a naphtylgroup.

R^(b), R^(c) and R^(d), equal to or different from each other, arehydrogen atoms, halogen atoms, linear or branched, saturated orunsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms,or two or more adjacent substituents R^(b), R^(c), and R^(d) form one ormore C₄-C₇ rings, optionally containing O, S, N, P or Si atoms, that canbear substituents; with b) a Lewis acid of formula (I)MtR¹ ₃   (II)wherein Mt is a metal belonging to Group 13 of the Periodic Table of theElements (IUPAC); R¹, equal to or different from each other, are halogenatoms, halogenated C₆-C₂₀ aryl and halogenated C₇-C₂₀ alkylaryl groups;two R¹ groups can also form with the metal Mt one condensed ring, suchas for example 9-borafluorene compounds.

Preferably Mt is B or Al, and more preferably is B; the substituents R¹are C₆F₅, C₆F₄H, C₆F₃H₂, C₆H₃(CF₃)₂, perfluoro-biphenyl,heptafluoro-naphthyl, hexafluoro-naphthyl and pentafluoro-naphthyl; mostpreferred R¹ substituents are C₆F₅ radicals.

Preferred organometallic compounds are those belonging to the followingtwo classes (1) and (2), having respectively formula (III) and (IV).

Class (1)

Organometallic compounds belonging to class (1) have the followingformula (III)

wherein

Mt is a metal belonging to Group 13 of the Periodic Table of theElements (IUPAC); R¹, equal to or different from each other, are halogenatoms, halogenated C₆-C₂₀ aryl or halogenated C₇-C₂₀ alkylaryl groups;or two R¹ groups can form with the metal Mt one condensed ring, such asfor example 9-borafluorene compounds; the substituents R⁵, R⁴ and R³equal to or different from each other, are hydrogen atoms, halogenatoms, linear or branched, saturated or unsaturated, C₁-C₁₀ alkyl,C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl groups, optionallycontaining O, S, N, P, Si or halogen atoms, or two or more adjacentsubstituents R³, R⁴ and R⁵ form one or more C₄-C₇ rings, optionallycontaining O, S, N, P or Si; preferably R⁴ and R⁵ form one condensedC₅-C₆ aromatic ring, optionally containing O, S, N, or P atoms, thatreplace one or more carbons of the aromatic ring and can bearsubstituents; preferably R³ is hydrogen;

R² is a linear or branched, saturated or unsaturated, C₁-C₁₀ allyl,C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl group, optionallycontaining O, S, N, P, Si or halogen atoms or R² can join R⁵ to form aC₄-C₇ ring; preferably R² is a C₁-C₁₀ alkyl, or C₆-C₂₀ aryl group; morepreferably R² is methyl, ethyl, propyl, phenyl or a naphtyl group.

Preferably in the organometallic compounds of formula (III) Mt is B orAl, and more preferably is B; the substituents R¹ equal to or differentfrom each other, C₆F₅, C₆F₄H, C₆F₃H₂, C₆H₃(CF₃)₂, perfluoro-biphenyl,heptafluoro-naphthyl, hexafluoro-naphthyl and pentafluoro-naphthyl; evenmore preferably, R¹ is C₆F₅.

A preferred subclass of organometallic compounds of formula (III) isthat of formula (V):

wherein

B is a boron atom;

the substituents R¹, R² and R³ have the meaning reported above and thesubstituents R⁶, the same or different from each other, are hydrogenatoms, halogen atoms, linear or branched, saturated or unsaturated,C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl groupsoptionally containing O, S, N, P, Si or halogen atoms, or two or moreadjacent substituents R⁶ form one or more C₄-C₇ rings, optionallycontaining O, S, N, P or Si atoms that can bear substituents;preferably, R⁶ are selected from the group consisting of hydrogen atoms,halogen atoms, and linear or branched, saturated or unsaturated C₁-C₁₀alkyl.

Class (2)

Organometallic compounds belonging to class (2) have the followingformula (IV):

wherein

Mt and R¹ are defined as above;

the substituents R^(3′), R^(4′) and R^(5′) equal to or different fromeach other, are hydrogen atoms, halogen atoms, linear or branched,saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl orC₇-C₂₀ alkylaryl groups, optionally containing O, S, N, P, Si or halogenatoms, or two or more adjacent substituents R^(3′), R^(4′) and R^(5′)form one or more C₄-C₇ rings optionally containing O, S, N, P or Siatoms, that can bear substituents; said rings can be aliphatic oroptionally can contain double bonds;

R^(2′) is a linear or branched, saturated or unsaturated, C₁-C₁₀ alkyl,C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl group, optionallycontaining O, S, N, P, Si or halogen atoms; or R^(2′) can join R^(5′) toform a C₄-C₇ ring; preferably R^(2′) is a C₁-C₁₀ alkyl, or C₆-C₂₀ arylgroup; more preferably R^(2′) is methyl, ethyl, propyl, tertbutyl,phenyl or a naphtyl group.

Preferably the substituents R^(3′), R^(4′) and R^(5′), are hydrogenatoms, linear or branched, saturated or unsaturated, C₁-C₁₀ alkyl,optionally containing O, S, N, P, Si or halogen atoms, or two or moreadjacent substituents R^(3′), R^(4′) and R^(5′) form one or more C₄-C₇rings optionally containing O, S, N, P or Si atoms, that can bearsubstituents; said rings can be aliphatic or optionally can containsdouble bonds, with the proviso that said rings are not aromatic.

A preferred subclass of organometallic compounds of formula (IV) is thatof formula (VI):

wherein

the substituents R¹ and R^(2′) have the meaning described above and thesubstituent R^(5′) is a C₁-C₁₀ alkyl group; preferably R^(5′) is amethyl or ethyl group.

The organometallic compounds of the invention are easily prepared byreacting, in about stoichiometric amounts, a compound having the formula(I):

wherein R^(a), R^(b), R^(c) R^(d) and R^(e) are described above; with aLewis acid of formula (II)MtR¹ ₃   (II)wherein Mt and R¹ are described above.

The reaction between said Lewis acid and the compound of formula (I) ispreferably carried out in an aprotic solvent, even more preferably in apolar aprotic solvent (such as toluene, diethyl ether or CH₂Cl₂), atroom temperature, the reaction can be carried out also in the presenceof a small amount of water, preferably less than one molar equivalentwith respect to the Lewis acid.

A further object of the present invention is a salt obtainable bycontacting, in any order:

-   -   a) a compound having formula (I) as described above;    -   b) a Lewis acid of formula (II) as described above; and    -   c) a compound of formula KR^(f) ₃ wherein K is a nitrogen (N) or        phosphorous (P) atom; preferably K is nitrogen; R^(f), equal to        or different from each other, are linear or branched, saturated        or unsaturated, C₁-C₃₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl and        C₇-C₂₀ alkylaryl groups, optionally containing O, S, N, P, Si or        halogen atoms, or two R^(f) can form one C₄-C₇ ring, optionally        containing O, S, N, P or Si atoms, that can bear substituents;        preferably R^(f) is selected from the group consisting of linear        or branched, saturated or unsaturated, C₁-C₃₀ alkyl.

This salt can be used as cocatalyst for the polymerization of olefins.

Preferred salts compounds are those belonging to the following twoclasses (3) and (4), having respectively formulas (VII) and (VIII).

Class (3)

Salts belonging to class (3) have formula (VI):

wherein R¹, R², R³, R⁴, R⁵, Mt, K and R^(f) have the meaning describedabove.

A preferred subclass of salts of formula (VII) is that of formula (IX):

wherein R¹, R², R³, R⁶, B, K and R^(f) have the meaning described above.Class (4)

Salts belonging to class (4) have formula (VIII):

wherein R¹, R^(2′), R^(3′), R^(4′), R^(5′), Mt, K and R^(f) have themeaning described above.

A preferred subclass of salts of formula (VIII) is that of formula (X):

wherein R¹, R^(2′), R^(5′), Mt, K and R^(f) have the meaning describedabove.

A process for preparing the above described salts comprises thefollowing steps:

-   -   a) contacting at least one equivalent of a compound of        formula (I) with one equivalent of a Lewis acid of formula (II),        wherein the compound of formula (I) and (II) has been described        above; and    -   b) optionally isolating the reaction product of step a) and then        adding at least one equivalent of a compound of formula KR^(f)        ₃, wherein K and R^(f) have been described above.

The two steps described above can be carried out both by isolating theintermediate product formed in step a), generally by filtration orevaporation of the solvent, or carried out “one pot” without isolatingthe intermediate product; preferably the reaction is carried out in anaprotic solvent, even more preferably in a polar aprotic solvent (suchas toluene, diethyl ether or CH₂Cl₂), at room temperature. The reactioncan be carried out also in the presence of little amount of water,preferably equal to or less than one molar equivalent with respect tothe Lewis acid. The final product is generally isolated by filtration orevaporation of the solvent. An alternative process for preparing theabove described salts comprises the step of contacting a compound offormula (III), (IV), (V) or (VI) with at least one equivalent of acompound of formula KR^(f) ₃, wherein K and R^(f) have been describedabove.

Non limitative examples of compounds belonging to formula (I) are:N-methyl-pyrrole; N-methyl-2-ethylpyrrole; N-methyl-2,4-dimethylpyrrole;N-methyl-4,5,6,7-tetrahydroindole; N-methyl-2,4-dimethyl-3-ethylpyrrole;N-methyl-indole; N-methyl-3-methylindole; N-methyl-4-methylindole;N-methyl-5-methylindole; N-methyl-6-methylindole;N-methyl-7-methylindole; N-methyl-5-fluoroindole;N-methyl-4-chloroindole; N-methyl-5-chloroindole;N-methyl-6-chloroindole; N-methyl-5-bromoindole;N-methyl-5-methoxyindole; N-methyl-4-methoxyindole;N-methyl-5,6-dimethoxyindole; N-methyl-5-benzyloxyindole; and thecorresponding N-ethyl, N-propyl, N-phenyl and N-naphtyl compounds.

Example of Lewis acid of formula (II) are:tris(pentafluorophenyl)borane; tris(heptafluoronaphthyl)borane;tris(2,3,5,6,7,8-hexafluoronaphthyl)borane;tris(2,4,5,6,7,8-hexafluoronaphthyl)borane;tris(3,4,5,6,7,8-hexafluoronaphthyl)borane;tris(2,3,4,6,7,8-hexafluoronaphthyl)borane;tris(2,3,4,5,7,8-hexafluoronaphthyl)borane;tris(2,3,5,6,7,8-hexafluoro-4-methylnaphthyl)borane;tris(2,4,5,6,7,8-hexafluoro-3-methylnaphthyl)borane;tris(3,4,5,6,7,8-hexafluoro-2-methylnaphthyl)borane;tris(2,3,4,6,7,8-hexafluoro-5-methylnaphthyl)borane;tris(2,3,4,5,7,8-hexafluoro-6-methylnaphthyl)borane;tris(nonafluorobiphenyl)borane;tris(2,2′,3,3′,5,5′,6,6′-octafluorobiphenyl)borane;tris(3,3′,4,4′,5,5′,6,6′-octafluorobiphenyl)borane;tris(2,2′,4,4′,5,5′,6,6′-octafluorobiphenyl)borane;tris(2,2′,3,3′,4,4′,6,6′-octafluorobiphenyl)borane;tris(2,2′,3,3′,4,4′,5,5′-octafluorobiphenyl)borane;tris(2,2′,3,3′,5,5′,6,6′-octafluorobiphenyl)borane;tris(3,3′,4,4′,5,5′,6,6′-octafluorobiphenyl)borane;tris(2,2′,4,4′,5,5′,6,6′-octafluorobiphenyl)borane;tris(2,2′,3,3′,4,4′,6,6′-octafluoro-5,5′-methylbiphenyl)borane;tris(2,2′,3,3′,4,4′,5,5′-octafluoro-6,6′-methylbiphenyl)borane;tris(2,2′,3,3′,5,5′,6,6′-octafluoro-4,4′-biphenyl)borane;tris(3,3′,4,4′,5,5′,6,6′-octafluoro-2,2′-biphenyl)borane;tris(2,2′,4,4′,5,5′,6,6′-octafluoro-3,3′-biphenyl)borane;tris(2,3,4,6-tetrafluorophenyl)borane;tris(2,3,5,6-tetrafluorophenyl)borane;tris(2,3,5-trifluorophenyl)borane, tris(2,3,6-trifluorophenyl)borane;tris(1,3-difluorophenyl)borane,tris(2,3,5,6-tetrafluoro-4-methylphenyl)borane;tris(2,3,4,6-tetrafluoro-5-methylphenyl)borane;tris(2,6-difluoro-3-methylphenyl)borane;tris(2,4-difluoro-5-methylphenyl)borane;tris(3,5-difluoro-2-methylphenyl)borane;fluorobis(pentafluorophenyl)borane; chlorobis(pentafluorophenyl)borane;dichloro(pentafluorophenyl)borane; difluoro (pentafluorophenyl)borane;9-chloro-9-boroperfluorofluorene; 9-methyl-9-boroperfluorpfluorene;9-pentafluorophenyl-9-boroperfluorofluorene and9-bromo-9-boroperfluorofluorene.

It is another object of the present invention a catalyst system for thepolymerization of olefins comprising the product obtained by contacting:

(A) at least one transition metal organometallic compound, and,

(B) an organometallic compound obtainable by contacting

-   -   -   a) a compound having the following formula (I):

    -   wherein R^(a), R^(b), R^(c) and R^(d) have the meaning described        above

    -   b) a Lewis acid of formula (II)        MtR¹ ₃   (II);

    -   wherein Mt and R¹ have the meaning described above; and

    -   c) optionally a compound of formula KR^(f) ₃, wherein K and        R^(f) have the meaning described above.

The catalyst system can optionally further comprise an alkylating agent.

Preferably the catalyst system of the present invention of olefinscomprises the product obtained by contacting:

-   -   (A) at least one transition metal organometallic compound;    -   (B) an organometallic compound belonging to class (1) (compounds        of formula (III), or (V)) or class (2) (compounds of        formula (IV) or (VI)) as described above or a salt belonging to        class (3) (salts of formula (VII) or (IX)) or class (4) (salts        of formula (VIII) or (X)).

The catalyst system can optionally further comprise an alkylating agent.

Transition metal organometallic compounds for use in the catalyst systemin accordance with the present invention are compounds suitable asolefin polymerization catalysts by coordination or insertionpolymerization. The class includes known transition metal compoundsuseful in traditional Ziegler-Natta coordination polymerization,metallocene compounds and the transition metal compounds known to beuseful in coordination polymerization. These typically include Group4-10 transition metal compounds wherein at least one metal ligand can beabstracted by the catalyst activators. As a rule, when said ligand ishydrogen or an hydrocarbyl group containing from 1 to 20 carbon atomsoptionally containing silicon atoms, the transition metal organometalliccatalyst compounds can be used as such, otherwise an alkylating agenthas to be used in order to alkylate said catalyst. The alkylation can becarried out in a separate step or in situ.

The alkylating agent is a compound able to react with the transitionmetal organometallic catalyst compounds and exchange said ligand thatcan be abstracted, with an alkyl group. Preferably said alkylating agentis selected from the group consisting of R¹⁰Li, R¹⁰Na, R¹⁰K, R¹⁰MgU orAlR¹⁰ _(3-z)W_(z), or alumoxanes, wherein R¹⁰ can be C₁-C₁₀ alkyl,alkenyl or alkylaryl radicals, optionally containing one or more Si orGe atoms, z is 0, 1 or 2 or a non integer number ranging from 0 to 2; Uis chlorine, bromine or iodine and W is hydrogen, chlorine, bromine oriodine atom; non-limiting examples of R¹⁰ are methyl, ethyl, butyl andbenzyl; non limiting example of AlR¹⁰ _(3-z)W_(z), compounds aretrimethylaluminum (TMA), tris(2,4,4-trimethyl-pentyl)aluminum (TIOA),tris(2-methyl-propyl)aluminum (TIBA),tris(2,3,3-trimethyl-butyl)aluminum, tris(2,3-dimethyl-hexyl)aluminum,tris(2,3-dimethyl-butyl)aluminum, tris(2,3-dimethyl-pentyl)aluminum,tris(2,3-dimethylheptyl)aluminum, tris(2-methyl-3-ethyl-pentyl)aluminumand tris(2-ethyl-3,3-dimethylbutyl). Non limiting example of alumoxanesare: methylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO),tetra-(2,4,4-trimethyl-pentyl)alumoxane (TIOAO),tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) andtetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO).

Different from the catalyst system disclosed in WO 99/64476, thecatalyst system of the present invention is stable and can be isolated.

A preferred class of transition metal organometallic compounds aremetallocene compounds belonging to the following formula (XI)(Cp)(ZR⁷ _(m))_(n)(A)_(r)ML_(p)   (XI)wherein (ZR⁷ _(m))_(n) is a divalent group bridging Cp and A; Z being C,Si, Ge, N or P, and the R⁷ groups, equal to or different from eachother, being hydrogen or linear or branched, saturated or unsaturatedC₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀arylalkyl groups or two R⁷ can form a aliphatic or aromatic C₄-C₇ ring;

Cp is a substituted or unsubstituted cyclopentadienyl group, optionallycondensed to one or more substituted or unsubstituted, saturated,unsaturated or aromatic rings, containing from 4 to 6 carbon atoms,optionally containing one or more heteroatoms;

A is O, S, NR⁸, PR⁸ wherein R⁸ is hydrogen, a linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl,C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkyl, or A has the same meaning of Cp;

M is a transition metal belonging to group 4, 5 or to the lanthanide oractinide groups of the Periodic Table of the Elements IUPAC version);

the substituents L, equal to or different from each other, aremonoanionic sigma ligands selected from the group consisting ofhydrogen, halogen, R⁹, OR⁹, OCOR⁹, SR⁹, NR⁹ ₂ and PR⁹ ₂, wherein R⁹ is alinear or branched, saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkyl group,optionally containing one or more Si or Ge atoms; preferably, thesubstituents L are the same;

m is 1 or 2, and more specifically it is 1 when Z is N or P, and it is 2when Z is C, Si or Ge;

n is an integer ranging from 0 to 4;

r is 0, 1 or 2; preferably 0 or 1; n is 0 when r is 0;

p is an integer equal to the oxidation state of the metal M minus r+1;i.e. minus 3 when r=2, minus 2 when r=1, and minus 1 when r=0, andranges from 1 to 4.

In the metallocene compound of formula (XI), the divalent bridge (ZR⁷_(m))_(n) is preferably selected from the group consisting of CR⁷ ₂,(CR⁷ ₂)₂, (CR⁷ ₂)₃, SiR⁷ ₂, GeR⁷ ₂, NR⁷ and PR⁷, R⁷ having the meaningreported above; more preferably, said divalent bridge is Si(CH₃)₂,SiPh₂, CH₂, (CH₂)₂, (CH₂)₃ or C(CH₃)₂.

The variable m is preferably 1 or 2; the variable n ranges preferablyfrom 0 to 4 and, when n>1, the atoms Z can be the same or different fromeach other, such as in divalent bridges CH₂—O, CH₂—S and CH₂—Si(CH₃)₂.

The ligand Cp, which is π-bonded to said metal M, is preferably selectedfrom the group consisting of cyclopentadienyl, mono-, di-, tri- andtetra-methyl cyclopentadienyl; 4-^(t)butyl-cyclopentadienyl;4-adamantyl-cyclopentadienyl; indenyl; mono-, di-, tri- and tetra-methylindenyl; 2-methyl indenyl, 3-^(t)butyl-indenyl, 2-methyl-4-phenylindenyl, 2-methyl-4,5 benzo indenyl; 3-trimethylsilyl-indenyl;4,5,6,7-tetrahydroindenyl; fluorenyl;5,10-dihydroindeno[1,2-b]indol-10-yl; N-methyl- orN-phenyl-5,10-dihydroindeno [1,2-b]indol-10-yl;5,6-dihydroindeno[2,1-b]indol-6-yl; N-methyl-orN-phenyl-5,6-dihydroindeno[2,1-b]indol-6-yl; azapentalene-4-yl;thiapentalene-4-yl; azapentalene-6-yl; thiapentalene-6-yl; mono-, di-and tri-methyl-azapentalene-4-yl,2,5-dimethyl-cyclopenta[1,2-b:4,3-b′]-dithiophene.

The group A is O, S, N(⁸), wherein R⁸ is hydrogen, a linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl,C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkyl, preferably R⁸ is methyl, ethyl,n-propyl, isopropyl, n-butyl, t-butyl, phenyl, p-n-butyl-phenyl, benzyl,cyclohexyl and cyclododecyl; more preferably R⁸ is t-butyl; or A has thesame meaning of Cp.

Non limiting examples of compounds belonging to formula (XI) are thefollowing compounds (when possible in either their meso or racemicisomers, or mixtures thereof): bis(cyclopentadienyl)zirconium dimethyl;bis(indenyl)zirconium dimethyl; bis(tetrahydroindenyl)zirconiumdimethyl; bis(fluorenyl)zirconium dimethyl;(cyclopentadienyl)(indenyl)zirconium dimethyl;(cyclopentadienyl)(fluorenyl)zirconium dimethyl;(cyclopentadienyl)(tetrahydroindenyl)zirconium dimethyl;(fluorenyl)(indenyl)zirconium dimethyl;dimethylsilanediylbis(indenyl)zirconium dimethyl,dimethylsilanediylbis(2-methyl-4-phenylindenyl)zirconium dimethyl,dimethylsilanediylbis(4-naphthylindenyl)zirconium dimethyl,dimethylsilanediylbis(2-methylindenyl)zirconium dimethyl,dimethylsilanediylbis(2-methyl-4-t-butylindenyl)zirconium dimethyl,dimethylsilanediylbis(2-methyl-4-isopropylindenyl)zirconium dimethyl,dimethylsilanediylbis(2,4-dimethylindenyl)zirconium dimethyl,dimethylsilanediylbis(2-methyl-4,5-benzoindenyl)zirconium dimethyl,dimethylsilanediylbis(2,4,7-trimethylindenyl)zirconium dimethyl,dimethylsilanediylbis(2,4,6-trimethylindenyl)zirconium dimethyl,dimethylsilanediylbis(2,5,6-trimethylindenyl)zirconium dimethyl,methyl(phenyl)silanediylbis(2-methyl-4,6-diisopropylindenyl)-zirconiumdimethyl,methyl(phenyl)silanediylbis(2-methyl-4-isopropylindenyl)-zirconiumdimethyl, 1,2-ethylenebis(indenyl)zirconium dimethyl,1,2-ethylenebis(4,7-dimethylindenyl)zirconium dimethyl,1,2-ethylenebis(2-methyl-4-phenylindenyl)zirconium dimethyl,1,4-butanediylbis(2-methyl-4-phenylindenyl)zirconium dimethyl,1,2-ethylenebis(2-methyl-4,6-diisopropylindenyl)zirconium dimethyl,1,4-butanediylbis(2-methyl-4-isopropylindenyl)zirconium dimethyl,1,4-butanediylbis(2-methyl-4,5-benzoindenyl)zirconium dimethyl,1,2-ethylenebis(2-methyl-4,5-benzoindenyl)zirconium dimethyl,[4-(η⁵-cyclopentadienyl)-4,6,6-trimethyl(η⁵-4,5-tetrahydro-pentalene)]dimethylzirconium,[4-(η⁵-3′-trimethylsilylcyclopentadienyl)-4,6,6-trimethyl(η⁵-4,5-tetrahydropentalene)]dimethylzirconium,(tert-butylamido)(tetramethyl-μ⁵-cyclopentadienyl)-1,2-ethane-dimethyltitanium,(methylamido)(tetramethyl-η⁵-cyclopentadienyl)dimethylsilyl-dimethyltitanium,(methylamido)(tetramethyl-η⁵-cyclopentadienyl)-1,2-ethanediyl-dimethyltitanium,(tertbutylamido)-(2,4-dimethyl-2,4-pentadien-1-yl)dimethylsilyl-dimethyltitanium,bis(1,3-dimethylcyclopentadienyl)zirconium dimethyl,methylene(3-methyl-cyclopentadienyl)-7-(2,5-ditnethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;methylene(3-isopropyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdi&ethyl;methylene(2,4-dimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;methylene(2,3,5-trimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;methylene-1-(indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl and dimethyl;methylene-1-(indenyl)-7-(2,5-ditrimethylsilylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;methylene-1-(3-isopropyl-indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;methylene-1-(2-methyl-indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;methylene-1-(tetrahydroindenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;methylene(2,4-dimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dioxazol)zirconiumdimethyl;methylene(2,3,5-trimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dioxazol)zirconiumdimethyl;methylene-1-(indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dioxazol)zirconiumdimethyl and dimethyl;isopropylidene(3-methyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;isopropyldene(2,4-dimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;isopropylidene(2,4-diethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;isopropylidene(2,3,5-trimethyl-cyclopentadienyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;isopropylidene-1-(indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;isopropylidene-1-(2-methyl-indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)zirconiumdimethyl;dimethylsilandiyl-1-(2-methyl-indenyl)-7-(2,5-dimethylcyclopentadienyl-[1,2-b:4,3-b′]dithiophene)hafniumdimethyl;dirnethylsilanediyl(3-tert-butyl-cyclopentadienyl)(9-fluorenyl)zirconiumdimethyl,dimethylsilanediyl(3-isopropyl-cyclopentadienyl)(9-fluorenyl)zirconiumdimethyl,dimethylsilanediyl(3-methyl-cyclopentadienyl)(9-fluorenyl)zirconiumdimethyl,dimethylsilanediyl(3-ethyl-cyclopentadienyl)(9-fluorenyl)zirconiumdimethyl,1-2-ethane(3-tert-butyl-cyclopentadienyl)(9-fluorenyl)zirconiumdimethyl, 1-2-ethane(3-isopropyl-cyclopentadienyl)(9-fluorenyl)zirconiumdimethyl, 1-2-ethane(3-methyl-cyclopentadienyl)(9-fluorenyl)zirconiumdimethyl, 1-2-ethane(3-ethyl-cyclopentadienyl)(9-fluorenyl)zirconiumdimethyl,dimethylsilandiylbis-6-(3-methylcyclopentadienyl-[1,2-b]-thiophene)dimethyl;dimethylsilandiylbis-6-(4-methylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdimethyl;dimethylsilandiylbis-6-(4-isopropylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdimethyl;dimethylsilandiylbis-6-(4-ter-butylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdimethyl;dimethylsilandiylbis-6-(3-isopropylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdimethyl;dimethylsilandiylbis-6-(3-phenylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdimethyl;dimethylsilandiylbis-6-(2,5-dimethyl-3-phenylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdi methyl;dimethylsilandiylbis-6-[2,5-dimethyl-3-(2-methylphenyl)cyclopentadienyl-[1,2-b]-thiophene]zirconiumdimethyl;dimethylsilandiylbis-6-[2,5-dimethyl-3-(2,4,6-trimethylphenyl)cyclopentadienyl-[1,2-b]-thiophene]zirconiumdimethyl;dimethylsilandiylbis-6-[2,5-dimethyl-3-mesitylenecyclopentadienyl-[1,2-b]-thiophene]zirconiumdimethyl;dimethylsilandiylbis-6-(2,4,5-trimethyl-3-phenylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdimethyl;dimethylsilandiylbis-6-(2,5-diethyl-3-phenylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdimethyl;dimethylsilandiylbis-6-(2,5-diisopropyl-3-phenylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdimethyl;dimethylsilandiylbis-6-(2,5-diter-butyl-3-phenylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdimethyl;dimethylsilandiylbis-6-(2,5-ditrinethylsilyl-3-phenylcyclopentadienyl-[1,2-b]-thiophene)zirconiumdimethyl;dimethylsilandiylbis-6-(3-methylcyclopentadienyl-[1,2-b]-silole)zirconiumdimethyl;dimethylsilandiylbis-6-(3-isopropylcyclopentadienyl-[1,2-b]-silole)zirconiumdimethyl;dimethylsilandiylbis-6-(3-phenylcyclopentadienyl-[1,2-b]-silole)zirconiumdimethyl;dimethylsilandiylbis-6-(2,5-dimethyl-3-phenylcyclopentadienyl-[1,2-b]-silole)zirconiumdimethyl;dimethylsilandiylbis-6-[2,5-dimethyl-3-(2-methylphenyl)cyclopentadienyl-[1,2-b]-silole]zirconiumdimethyl;dimethylsilandiylbis-6-[2,5-dimethyl-3-(2,4,6-trimethylphenyl)cyclopentadienyl-[1,2-b]-silole]zirconiumdimethyl;dimethylsilandiylbis-6-[2,5-dimethyl-3-mesitylenecyclopentadienyl-[1,2-b]-silole]zirconiumdimethyl;dimethylsilandiylbis-6-(2,4,5-trimethyl-3-phenylcyclopentadienyl-[1,2-b]-silole)zirconiumdimethyl;[dimethylsilyl(tert-butylamido)][(N-methyl-1,2-dihydrocyclopenta[2,1-b]indol-2-yl)]titaniumdimethyl;[dimethylsilyl(tert-butylamido)][(6-methyl-N-methyl-1,2-dihydrocyclopenta[2,1-b]indol-2-yl)]titaniumdimethyl;[dimethylsilyl(tert-butylamido)][(6-methoxy-N-methyl-1,2-dihydrocyclopenta[2,1-b]indol-2-yl)]titaniumdimethyl;[dimethylsilyl(tert-butylamido)][(N-ethyl-1,2-dihydrocyclopenta[2,1-b]indol-2-yl)]titaniumdimethyl;[dimethylsilyl(tert-butylamido)][(N-phenyl-1,2-dihydrocyclopenta[2,1-b]indol-2-yl)]titaniumdimethyl;[dimethylsilyl(tert-butylamido)][(6-methyl-N-phenyl-1,2dihydrocyclopenta[2,1-b]indol2-yl)]titaniumdimethyl;[dimethylsilyl(tert-butylamido)][(6-methoxy-N-phenyl-1,2-dihydrocyclopenta[2,1-b]indol2-yl)]titaniumdimethyl;[dimethylsilyl(tert-butylamido)][(N-methyl-3,4-dimethyl-1,2-dihydrocyclopenta[2,1-b]indol-2-yl)]titaniumdimethyl;[dimethylsilyl(tert-butylamido)][(N-ethyl-3,4-dimethyl-1,2-dihydrocyclopenta[2,1-b]indol-2-yl)]titaniumdimethyl;[dimethylsilyl(tert-butylamido)][(N-phenyl-3,4-dimethyl-1,2-dihydroclopenta[2,1-b]indol-2-yl)]titaniumdimethyl; as well as the corresponding dichloro, hydrochloro and dihydrocompounds and the corresponding η⁴⁻butadiene compounds.

When A is N(R⁸), a suitable class of metallocene complexes (A) for usein the catalysts complexes of the invention comprises the well-knownconstrained geometry catalysts, as described in EP-A-0 416 815, EP-A-0420 436, EP-A-0 671 404, EP-A-0 643 066 and WO-A-91/04257.

A further preferred class of transition metal organometallic catalystcompounds are late transition metal complex of formula (XII) or (XIII)L^(a)M^(a)X^(a)p^(a)   (XII)L^(a)M^(a)A^(a)   (XIII)wherein M^(a) is a metal belonging to Group 8, 9, 10 or 11 of thePeriodic Table of the Elements (new IUPAC notation);

L^(a) is a bidentate or tridentate ligand of formula (XIV):

wherein:

-   -   Q is a C₁-C₅₀ bridging group linking E¹ and E², optionally        containing one or more atoms belonging to Groups 13-17 of the        Periodic Table;

E¹ and E², the same or different from each other, are elements belongingto Group 15 or 16 of the Periodic Table and are bonded to said metalM^(a);

the substituents R^(a1), equal to or different from each other, areselected from the group consisting of hydrogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl,C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals, optionally containingone or more atoms belonging to groups 13-17 of the Periodic Table of theElements (such as B, Al, Si, Ge, N, P, O, S, F and Cl atoms); or twoR^(a1) substituents attached to the same atom E¹ or E² form a saturated,unsaturated or aromatic C₄-C₇ ring, having from 4 to 20 carbon atoms;

m^(a) and n^(a) are independently 0, 1 or 2, depending on the valence ofE¹ and E², so to satisfy the valence number of E¹ and E²; q^(a) is thecharge of the bidentate or tridentate ligand so that the oxidation stateof M^(a)X^(a) _(p)X^(a′) _(s) or M^(a)A^(a) is satisfied, and thecompound (XII) or (XIII) is overall neutral;

X^(a), the same or different from each other, are monoanionic sigmaligands selected from the group consisting of hydrogen, halogen, R^(a),OR^(a), OSO₂CF₃, OCOR^(a), SR^(a), —NR₂ and PR^(a) ₂ groups, wherein theR^(a) substituents are linear or branched, saturated or unsaturated,C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀arylalkyl radicals, optionally containing one or more atoms belonging togroups 13-17 of the Periodic Table of the Elements (new IUPAC notation),such as B, N, P, Al, Si, Ge, O, S and F atoms; or two X^(a) groups forma metallacycle ring containing from 3 to 20 carbon atoms; thesubstituents X^(a) are preferably the same;

p^(a) is an integer ranging from 0 to 3, so that the final compound(XII) or (XIII) is overall neutral; and

A^(a) is a π-allyl or a π-benzyl group.

Non limiting examples of late transition metal complexes are thosedescribed in WO 96/23010, WO 97/02298, WO 98/40374 and J. Am. Chem. Soc.120:4049-4050, 1998. Brookhart et al, J. Am. Chem. Soc. 1995, 117, 6414and Brookhart et al, J. Am. Chem. Soc., 1996, 118, 267, Brookhart et al,J. Am. Chem. Soc. 1998, 120, 4049, Gibson et al, Chem. Commun. 1998,849, WO 96/27439 and Chem. Ber./Recl. (1997), 130(3), 399-403. Theorganometallic compounds and the salts according to the invention exertgood activities as cocatalysts in olefin polymerization process;moreover, they are easy to prepare and do not lead to the release ofundesired by-products after the metallocene activation. Further they arestable and produce stable catalyst compositions under polymerizationconditions.

The molar ratio between the component (B) and the transition metalorganometallic compound (A), calculated as the molar ratio between themetal Mt of the Lewis acid and the metal of the transition metalorganometallic catalyst compound, preferably ranges from 10:1 to 1:10,more preferably from 2:1 to 1:2, and even more preferably is about 1:1.

According to the invention, component (B) of the catalyst system cansuitably comprise a mixture of two or more organometallic compounds orsalts of the invention. Moreover, component (B) can be used incombination with other compatible cocatalysts known in the state of theart, such as alumoxane compounds.

The catalyst system of the invention may also comprise one or morealuminum compounds of formula AlR¹⁰ _(3-z)W_(z), acting as scavenger,wherein R¹⁰ can be C₁-C₁₀ alkyl, alkenyl or alkylaryl radicals,optionally containing one or more Si or Ge atoms, z is 0, 1 or 2 or anon integer number ranging from 0 to 2; W is hydrogen, chlorine, bromineor iodine; non-limiting examples of aluminum compounds aretrimethylaluminum (TMA), tris(2,4,4-trimethyl-pentyl)aluminum (TIOA),tris(2-methyl-propyl)aluminum (TIBA),tris(2,3,3-trimethyl-butyl)aluminum, tris(2,3-dimethyl-hexyl)aluminum,tris(2,3-dimethyl-butyl)aluminum, tris(2,3-dimethyl-pentyl)aluminum,tris(2,3-dimethyl-heptyl)aluminum, tris(2-methyl-3-ethyl-pentyl)aluminumand tris(2-ethyl-3,3-dimethyl-butyl).

Another example of compound that can act as scavenger are alumoxanecompounds containing at least one group of the type:

wherein the R¹¹ substituents, which may be the same or different, aredescribed above. In particular, alumoxanes of the formula:

can be used in the case of linear compounds, wherein n¹ is 0 or aninteger from 1 to 40 and the R¹¹ substituents are defined as above, oralumoxanes of the formula:

can be used in the case of cyclic compounds, wherein n² is an integerfrom 2 to 40 and the R¹¹ substituents are defined as above.

Examples of alumoxanes suitable as scavenger according to the presentinvention are methylalumoxane (MAO), tetra-(isobutyl)alumoxane (TIBAO),tetra-(2,4,4-trimethyl-pentyl)alumoxane (TIOAO),tetra-(2,3-dimethylbutyl)alumoxane (TDMBAO) andtetra-(2,3,3-trimethylbutyl)alumoxane (TTMBAO).

Particularly interesting alumoxanes are those disclosed in WO 99/21899.

The catalyst system of the invention may be formed prior to itsintroduction into a polymerization reactor or in situ in the reactor, bycontacting the above-described components (A), (B) and optionally analkylating agent.

According to an embodiment of the invention, components (A), (B) andoptionally an alkylating agent are first contacted and then introducedinto the reactor, wherein separately an aluminum compound AlR¹⁰_(3-z)W_(z), or an alumoxane has been introduced. Alternatively,components (A), (B) and optionally an alkylating agent and said aluminumcompound AlR¹⁰ _(3-z)W_(z) or said alumoxane may be contacted togetherprior to their introduction into the reactor.

The catalysts system of the present invention can be used on inertsupports. This may be achieved by depositing said transition metalorganometallic catalyst compound (A), or the product of the reactionthereof with the component (B), or the component (B) and subsequentlysaid transition metal organometallic compound before or after theoptional treatment with said alkylating agent, on inert supports such assilica, alumina, styrene/divinylbenzene copolymers, polyethylene orpolypropylene.

The thus obtained solid compound can be suitably used in gas phasepolymerization.

The catalysts of the present invention can be used in the polymerizationreactions of olefins.

Therefore, according to a further object, the invention provides aprocess for the polymerization of one or more olefins comprisingcontacting one or more olefins under polymerization conditions in thepresence of a catalyst system as described above.

Olefins which can be polymerized with the process of the presentinvention are, for instance, α-olefins of formula CH₂═CHR, wherein R ishydrogen or a C₁-C₂₀ alkyl radical.

The catalysts according to the present invention can be convenientlyused in the homopolymerization of ethylene, in particular for thepreparation of HDPE, and in the copolymerization of ethylene, inparticular for the preparation of LLDPE. Suitable comonomers in ethylenecopolymers are a-olefins of formula CH₂═CHR′, wherein R′ is a linear,branched or cyclic C₁-C₂₀ alkyl radical or cycloolefins. Examples ofsuch olefins are propylene, 1-butene, 1-pentene, 4-methyl-1-pentene,1-hexene, 1-octene, allyl-cyclohexane, cyclopentene, cyclohexene,norbornene and 4,6-dimethyl-1-heptene.

Further suitable comonomers in said ethylene copolymers are polyenes, inparticular conjugated or non-conjugated, linear or cyclic dienes, suchas 1,4hexadiene, isoprene, 1,3-butadiene, 1,5-hexadiene and1,6-heptadiene.

The catalysts of the invention can be suitably used in propylenehomopolymerization, or copolymerization in particular for the productionof isotactic polypropylene.

Moreover, the catalysts of the invention can be suitably used in thepreparation of elastomeric copolymers of ethylene with α-olefins offormula CH₂═CHR″, wherein R″ is a C₁-C₁₀ alkyl radical, such aspropylene, 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene.; saidcopolymers may optionally contain minor proportions of units derivingfrom polyenes.

According to a further embodiment, the catalysts according to thepresent invention are used in the preparation of cycloolefin polymers.Monocyclic and polycyclic olefin monomers can be either homopolymerizedor copolymerized, also with linear olefin monomers.

The polymerization processes of the present invention can be carried outin liquid phase, optionally in the presence of an inert hydrocarbonsolvent, or in gas phase. Said hydrocarbon solvent can be eitheraromatic (such as toluene) or aliphatic (such as propane, hexane,heptane, isobutane, cyclohexane and 2,2,4-trimethylpentane).

The polymerization temperature preferably ranges from 0° C. to 250° C.;in the preparation of HDPE and LLDPE, it is preferably comprised between20° C. and 150° C. and, more particularly between 40° C. and 90° C.; inthe preparation of elastomeric copolymers, it is preferably comprisedbetween 0° C. and 200° C., and more preferably between 20° C. and 100°C. The molecular weight of the polymers can be varied simply by varyingthe polymerization temperature, the type or the concentration of thecatalyst components, or by using molecular weight regulators, such ashydrogen.

The molecular weight distribution can be varied by using mixtures ofdifferent metallocene complexes or by carrying out the polymerization inseveral stages which differ in the polymerization temperature and/or theconcentrations of molecular weight regulator.

The polymerization yield depends on the purity of the transition metalorganometallic catalyst compound (A) in the catalyst, therefore, saidcompound can be used as such or can be subjected to purificationtreatments before use.

The following examples are given for illustrative and not limitingpurposes.

General Procedures and Characterizations

All operations were performed under nitrogen by using conventionalSchlenk-line techniques. Solvents were purified by degassing with N₂ andpassing over activated (8 hours, N₂ purge, 300° C.) Al₂O₃, and storedunder nitrogen. Indole (Aldrich, purity 98% or Fluka, purity 99%/o),N-methylindole (Aldrich, purity 97%), N-methylpyrrole (Aldrich, purity99%), NEt₃ (Aldrich, 99.5%) and B(C₆F₅)₃ (Boulder Scientific Company)were used as received.

¹H-NMR and ¹³C-NMR

The proton and carbon spectra of the compounds were obtained using aBruker DPX 200 spectrometer operating in the Fourier transform mode atroom temperature at 200.13 MHz and 50.33 MHz respectively. The sampleswere dissolved in CD₂Cl₂ or C₆D₆. As reference the residual peak ofCHDCl₂ or C₆HD₅ in the ¹H spectra (5.35 ppm and 7.15 ppm, respectively)and the peak of the solvent in the ¹³C spectra (53.80 ppm for CD₂Cl₂ and128.00 ppm for C₆D₆) were used. Proton spectra were acquired with a 15°pulse and 2 seconds of delay between pulses; 32 transients were storedfor each spectrum. The carbon spectra were acquired with a 45° pulse and6 seconds of delay between pulses; about 512 transients were stored foreach spectrum. CD₂Cl₂ (Aldrich, 99.8% atom D) was used as received,while C₆D₆ (Aldrich, 99% atom D) was dried over activated 4 A° molecularsieves before use. Preparation of the samples was carried out undernitrogen using standard inert atmosphere techniques.

Synthesis of the Organometallic Boron Compounds

EXAMPLE 1 Synthesis of2-[tris(pentafluorophenyl)borane]-3H-1-methylindole [A-1]

A yellow solution of 1-methylindole (97%, 0.78 g, MW=131.18, 5.8 nunol)in 10 ml of dichloromethane was added at room temperature to a whitesuspension of B(C₆F₅)₃ (99.4%, 2.97 g, MW=511.99, 5.8 inmol) in 10 ml ofdichloromethane in a 25 mL Schlenk flask. The resulting orange solutionwas stirred at room temperature for ten days and analyzed by ¹H NMR atdifferent times. During this time the color of the solution turned fromorange to dark bordeaux; NMR analyses showed a slow conversion of thestarting 1-methylindole to the product. The solvent was evaporated invacuum and the obtained solid was suspended in a 9/1pentane/dicloromethane mixture and filtered. The residue on the frit wasa fuchsia solid (3.27 g, yield 87.8%).

The product was completely characterized by ¹H NMR, ¹³C NMR, DEPT(Distorsionless Enhancement by Polarization Transfer), NOESY (NuclearOverhauser Enhancement Spectroscopy), COSY (Correlation Spectroscopy),HSQC (Heteronuclear Single Quantum Coherence) and HMBC (HeteronuclearMultiple Bond Correlation) analyses.

¹H NMR (CD₂Cl₂, δ, ppm): 3.77 (s, 3H, N—CH₃); 4.59 (broad AB system,2H3,H3′); 7.47-7.69 (m, 4H, Ar).

¹H NMR (C₆D₆, δ, ppm): 2.84 (s, 3H, N—CH₃); 4.04 (broad AB system, 2H,H3,H3′); 6.42-6.51 (m, 1H, H7); 6.83-6.98 (m, 3H, Ar).

¹³C NMR (CD₂Cl₂, δ, ppm): 36.55 (CH₃); 48.33 (C3); 113.59 (C7); 125.22(C4); 128.97 (C5 or C6); 129.22 (C6 or C5); 134.18 (C3a); 147.06 (C7a);214.34-217.43 (m, C2).

melting point 126.7° C.-127.8° C.

EXAMPLE 2 Synthesis oftris(pentafluorophenyl)-(1-methylindol-2-yl)-borate(1-)triethylammonium[A-2]

A colorless solution of triethylamine (99.5%, 0.167 g, MW=101.19, 1.6mmol) (dichloromethane, 6 mL) was added at room temperature to abordeaux solution of 2-[tris(pentafluorophenyl)borane]-3H-1-methylindole(1.048 g, MW=643.16, 1.6 mmol) (dichloromethane, 4 mL) in a 10 mLSchlenk flask. The resulting solution was stirred at room temperaturefor an hour and its color turned from the initially orange to yellow.Then the solvent was removed in vacuum to give a yellow solid asproduct, 1.11 g, yield 93.2%).

¹H NMR (CD₂Cl₂, δ, ppm): 1.03 (t, 9H, J=7.24 Hz, N(CH₂CH₃)₃); 2.60 (q,6H, J=7.24 Hz, N(CH₂CH₃)₃); 3.40 (bs, 1H, NH); 3.51 (s, 3H, N—CH₃); 6.19(s, 1H, H3); 6.95-7.13 (m, 2H, H5,H6); 7.23-7.29 (m, 1H, H7); 7.41-7.48(m, 1H, H4).

¹³C NMR (CD₂Cl₂, δ, ppm): 8.56 (N(CH₂CH₃)₃); 31.84 (N—CH₃); 47.32(N(CH₂CH₃)₃); 104.75 (C3); 109.35 (C7); 118.29 and 118.35 (C4 and C5 orC6); 119.19 (C6 or C5); 128.79 (C3a); 139.47 (C7a).

EXAMPLE 3 Synthesis of2-[tris(pentafluorophenyl)borane]-5H-1-methylpyrrole [A-3]

A light yellow solution of 1-methylpyrrole (99%, 0.503 g, MW=81.12, 6.1mmol) (dichloromethane, 10 mL) was added at room temperature to awhite-gray suspension of B(C₆F₅)₃ (99.4%, 3.18 g, MW=511.99, 6.2 mmol)(dichloromethane, 10 mL). The resulting orange cloudy solution wasstirred at room temperature for three days and then the solvent wasremoved under reduced pressure. The obtained orange powder was suspendedwith a ½ dichloromethane/pentane mixture and filtered. The filtrate wasa dark pink solid (the desired product together with unidentifiedspecies), whereas the residue on the frit was a very light yellow powder(2.42 g of the desired product, yield 66.5%).

¹H NMR (CD₂Cl₂, δ, ppm): 3.55 (s, 3H, CH₃); 4.70 (bs, 2H, H5,H5′); 6.91(bs, 1H, H3); 7.42 (d, J=5.87 Hz, 1H, H4).

¹³C NMR (CD₂Cl₂, δ, ppm): 38.12 (CH₃); 69.81 (C5); 108.42 (C2); 137.33(C3); 146.06 (C4). Melting point 116.6° C.-118.2° C.

EXAMPLE 4 Synthesis oftris(pentafluorophenyl)-(1-methypyrrol-2-yl)-borate(1-) triethylammonium[A-4]

A colorless solution of triethylamine (99.5%, 0.167 g, MW=101.19, 1.6mmol) (dichloromethane, 6 mL) was added at room temperature to an orangesolution of 2-[tris(pentafluorophenyl)borane]-5H-1-methylpyrrole [A-3](1.048 g, MW=643.16, 1.6 mmol) (dichloromethane, 6 mL) in a 25 mLSchlenk flask. The resulting light yellow solution was stirred at roomtemperature for an hour. Then the solvent was removed under reducedpressure to give a white-gray solid as product (0.892 g, yield 97.9%).

¹H NMR (CD₂Cl₂, δ, ppm): 1.22 (t, 9H, J=7.34 Hz, N(CH₂CH₃)₃); 3.03 (q,6H, J=7.34 Hz, N(CH₂CH₃)₃); 3.32 (s, 3H, N—CH₃); 5.76 (bd, 1H, J=2.64Hz, H3); 5.96 (d, 1H, J=3.23 Hz, H4); 6.10 (bs, 1H, NH); 6.64 (bs, 1H,H5).

¹³C NMR (CD₂Cl₂, δ, ppm): 8.82 (N(CH₂CH₃)₃); 35.94 (N—CH₃); 47.32(N(CH₂CH₃)₃); 104.40 (C4); 111.85 (C3); 122.95 (C5), 146.20 (C2).

Synthesis of bis(indenyl)zirconium dimethyl

29.6 mL of a solution of MeLi 1.6 M in Et₂O (47.4 mmol) were added atroom temperature to a solution of 3 g of indene (23.7 mmol, Aldrich,91.8 %) in 30 mL of Et₂O, over a period of about 5 minutes (exothermicreaction). The mixture was stirred for 30 minutes to give an orangesolution.

2.76 g of ZrCl₄ (11.84 mmol) were slurried in 30 mL of pentane. TheZrCl₄ slurry in pentane was quickly added to the Li salt solution inEt₂O (exothermic reaction). The resulting reaction mixture was stirredfor 2 hours and then brought to dryness under reduced pressure. Thelight brown solid obtained was extracted with 100 mL of pentane(Soxhlet, 4.5 hours) and then the filtrate was evaporated to drynessunder reduced pressure to give 3.2 g (77% yield) of a light yellowsolid, which was characterized by ¹H NMR as pure Ind₂ZrMe₂.

¹H-NMR (C₆D₆, δ, ppm): −0.78 (s, 6H, Zr—CH₃), 5.62 (t, 2H, Cp-H(2)),5.80 (d, 4H, Cp-H(1,3)); 6.87-6.92 (m, 4H, Ar), 7.19-7.23 (m, 4H, Ar).

Preparation of the Catalyst System

0.1 μmol of bis(indenyl)zirconium dimethyl prepared as reported above,was dissolved in 2 mL of toluene in a 10 mL Schlenk under nitrogenatmosphere and then the cocatalyst indicated in table 1 in 2 mL toluenewas quickly added (Zr/cocat molar ration 1:1.1).

POLYMERIZATION EXAMPLES 5-8

Ethylene Polymerization

Ethylene polymerizations were carried out in a 260-mL Büchi glassautoclave equipped with magnetic stirrer, thermocouple and feeding linefor the monomer, purified with nitrogen and kept in a thermostatic bath.Under ethylene purge, heptane (100 mL) and Al(i-Bu)₃ (0.1 mmol) wereintroduced, the temperature was brought to 80° C. and the reactor ventedto remove residual nitrogen, then pressurized with ethylene up to 0.5bar-g. The catalytic system, prepared as described above, was siphonedinto the reactor by means of a Teflon cannula, and the ethylene partialpressure was raised to 4 bar-g. The polymerization was carried out at80° C. for 15 minutes, by maintaining a constant ethylene partialpressure, then stopped by degassing the reactor and by adding 2 mL ofmethanol. The polymer was precipitated with 200 mL of acetone, filtered,washed with acetone and dried overnight at 60° C. reduced pressure. Thepolymerization results are reported in table 1. TABLE 1 ExampleCocatalyst yield (g) kg_(PE)/(mmol_(Zr) × h) 5 A-1 1.90 7.6 6 A-2 1.817.2 7 A-3 2.15 8.6 8 A-4 6.87 27.5

1. An organometallic compound obtained contacting: a) a compound havingthe following formula (I):

wherein R^(a) is a linear or branched, saturated or unsaturated, C₁-C₁₀alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl group,optionally containing O, S, N, P, Si or halogen atoms; or R^(a) can joinR^(d) to form a C₄-C₇ ring; R^(b), R^(c) and R^(d), equal to ordifferent from each other, are hydrogen atoms, halogen atoms, linear orbranched, saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀arylalkyl or C₇-C₂₀ alkylaryl groups, optionally containing O, S, N, P,Si or halogen atoms, or two or more adjacent substituents R^(b), R^(c),and R^(d) form one or more C₄-C₇ rings, optionally containing O, S, N, Por Si atoms, that can bear substituents; with b) a Lewis acid of formula(II):MtR¹ ₃   (II) wherein Mt is a metal belonging to Group 13 of thePeriodic Table of the Elements; R¹, equal to or different from eachother, are halogen atoms, halogenated C₆-C₂₀ aryl or ahalogenated C₇-C₂₀alkylaryl groups; two R¹ groups can also form with the metal Mt onecondensed ring.
 2. The organometallic compound according to claim 1wherein Mt is B or Al; and the substituents R¹ are C₆F₅, C₆F₄H, C₆F₃H₂,C₆H₃(CF₃)₂, perfluoro-biphenyl, heptafluoro-naphthyl,hexafluoro-naphthyl or pentafluoro-naphthyl.
 3. The organometalliccompound according to claim 1 having formula (III):

wherein Mt is a metal belonging to Group 13 of the Periodic Table of theElements (IUPAC); R¹, equal to or different from each other, are halogenatoms, halogenated C₆-C₂₀ aryl or halogenated C₇-C₂₀ alkylaryl groups;or two R¹ groups can form with the metal Mt one condensed ring; thesubstituents R⁵, R⁴ and R³ equal to or different from each other, arehydrogen atoms, halogen atoms, linear or branched, saturated orunsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms,or two or more adjacent substituents R³, R⁴ and R⁵ form one or moreC₄-C₇ rings, optionally containing O, S, N, P or Si; R² is a linear orbranched, saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀arylalkyl or C₇-C₂₀ alkylaryl group, optionally containing O, S, N, P,Si or halogen atoms or R² can join R⁵ to form a C₄-C₇ ring.
 4. Theorganometallic compound according to claim 3 wherein Mt is B or Al; thesubstituents R¹, equal to or different from each other, are C₆F₅, C₆F₄H,C₆F₃H₂, C₆H₃(CF₃)₂, perfluoro-biphenyl, heptafluoro-naphthyl,hexafluoro-naphthyl or pentafluoro-naphthyl; R⁴ and R⁵ form one C₅-C₆aromatic ring, optionally containing O, S, N, or P atoms, that can bearsubstituents; R² is a C₁-C₁₀ alkyl or C₆-C₂₀ aryl group; and R³ ishydrogen.
 5. The organometallic compound according to claim 3 havingformula (V):

wherein B is a boron atom; the substituents R⁶, the same or differentfrom each other, are hydrogen atoms, halogen atoms, linear or branched,saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl orC₇-C₂₀ alkylaryl groups optionally containing O, S, N, P, Si or halogenatoms, or two or more adjacent substituents R⁶ form one or more C₄-C₇,optionally containing O, S, N, P or Si atoms rings that can bearsubstituents.
 6. The organometallic compound according to claim 1 havingformula (IV):

wherein the substituents R^(3′), R^(4′) and R^(5′), equal to ordifferent from each other, are hydrogen atoms, halogen atoms, linear orbranched, saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀arylalkyl or C₇-C₂₀ alkylaryl groups, optionally containing O, S, N, P,Si or halogen atoms, or two or more adjacent substituents R^(3′), R^(4′)and R^(5′) form one or more C₄-C₇ rings, optionally containing O, S, N,P or Si atoms, that can bear substituents; said rings can be aliphaticand optionally contain double bonds; with the proviso that said ringsare not aromatic; R^(2′) is a linear or branched, saturated orunsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀alkylaryl group, optionally containing O, S, N, P, Si or halogen atoms;or R^(2′) can join R^(5′) to form a C₄-C₇ ring.
 7. The organometalliccompound according to claim 6 wherein R^(2′) is a C₁-C₁₀ alkyl, orC₆-C₂₀ aryl group; the substituents R^(3′), R^(4′) and R^(5′), equal toor different from each other, are hydrogen atoms, linear or branched,saturated or unsaturated, C₁-C₁₀ alkyl, optionally containing O, S, N,P, Si or halogen atoms, or two or more adjacent substituents R^(3′),R^(4′) and R^(5′) form one or more C₄-C₇ rings optionally containing O,S, N, P or Si atoms, that can bear substituents; said rings can bealiphatic and optionally contain double bonds, with the proviso thatsaid rings are not aromatic.
 8. The organometallic compound according toclaim 6 having formula (VI):

wherein the substituent R^(5′) is a C₁-C₂₀ alkyl group.
 9. A saltobtained by contacting, in any order: a) a compound having formula (I):

wherein R^(a) is a linear or branched, saturated or unsaturated, C₁-C₁₀alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl group,optionally containing O, S, N, P, Si or halogen atoms; or R^(a) can joinR^(d) to form a C₄-C₇ ring; R^(b), R^(c) and R^(d), equal to ordifferent from each other, are hydrogen atoms, halogen atoms, linear orbranched, saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀arylalkyl or C₇-C₁₀ alkylaryl groups, optionally containing O, S, N, P,Si or halogen atoms, or two or more adjacent substituents R^(b), R^(c),and R^(d) form one or more C₄-C₇ rings, optionally containing O, S, N, Por Si atoms, that can bear substituents; b) a Lewis acid of formula(II):MtR¹ ₃   (II) wherein Mt is a metal belonging to Group 13 of thePeriodic Table of the Elements; R¹, equal to or different from eachother, are halogen atoms, halogenated C₆-C₂₀ aryl or halogenated C₇-C₂₀alkylaryl groups; two R¹ groups can also form with the metal Mt onecondensed ring; and c) a compound of formula KR^(f) ₃ wherein K is anitrogen (N) or phosphorous (P) atom; R^(f), equal to or different fromeach other, are linear or branched, saturated or unsaturated, C₁-C₃₀alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl groups,optionally containing O, S, N, P, Si or halogen atoms, or two R^(f) canform one C₄-C₇ ring, optionally containing O, S, N, P or Si atoms, thatcan bear substituents.
 10. The salt according to claim 9 wherein K isnitrogen; and R^(f) is selected from the group consisting of linear orbranched, saturated or unsaturated, C₁-C₃₀ alkyl.
 11. The salt accordingto claim 9 having formula (VII):

wherein R¹, equal to or different from each other, are halogen atoms,halogenated C₆-C₂₀ aryl or halogenated C₇-C₂₀ alkylaryl groups; or twoR¹ groups can form with the metal Mt one condensed ring; thesubstituents R⁵, R⁴ and R³, equal to or different from each other, arehydrogen atoms, halogen atoms, linear or branched, saturated orunsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms,or two or more adjacent substituents R³, R⁴ and R⁵ form one or moreC₄-C₇ rings, optionally containing O, S, N, P or Si; R² is a linear orbranched, saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀arylalkyl or C₇-C₁₀ alkylaryl group, optionally containing O, S, N, P,Si or halogen atoms or R² can join R⁵ to form a C₄-C₇ ring.
 12. The saltaccording to claim 11 having formula (IX):

wherein B is a boron atom.
 13. The salt according to claim 9 havingformula (VIII):

wherein R¹, equal to or different from each other, are halogen atoms,halogenated C₆-C₂₀ aryl or halogenated C₇-C₁₀ alkylaryl groups: two R¹groups can also form with the metal Mt one condensed ring, thesubstituents R^(3′), R^(4′) and R^(5′), equal to or different from eachother, are hydrogen atoms, halogen atoms, linear or branched, saturatedor unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms,or two or more adjacent substituents R^(3′), R^(4′) and R^(5′) form oneor more C₄-C₇ rings, optionally containing O, S, N, P or Si atoms, thatcan bear substituents; said rings can be aliphatic and optionallycontain double bonds, with the proviso that said rings are not aromatic;R^(2′) is a linear or branched, saturated or unsaturated, C₁-C₁₀ alkyl,C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl group, optionallycontaining O, S, N, P, Si or halogen atoms; or R^(2′) can join R^(5′) toform a C₄-C₇ ring.
 14. The salt according to claim 13 having formula(X):

wherein B is a boron atom.
 15. A catalyst system for the polymerizationof olefins comprising the product obtained by contacting: (A) at leastone transition metal organometallic compound, and (B) an organometalliccompound obtained by contacting: a) a compound having the followingformula (I):

wherein R^(a) is a linear or branched, saturated or unsaturated, C₁-C₁₀alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl group,optionally containing O, S, N, P, Si or halogen atoms; or R^(a) can joinR^(d) to form a C₄-C₇ ring; R^(b), R^(c) and R^(d), equal to ordifferent from each other, are hydrogen atoms, halogen atoms, linear orbranched, saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀arylalkyl or C₇-C₂₀ alkylaryl groups, optionally containing O, S, N, P,Si or halogen atoms, or two or more adjacent substituents R^(b), R^(c),and R^(d) form one or more C₄-C₇ rings, optionally containing O, S, N, Por Si atoms, that can bear substituents; b) a Lewis acid of formula(II):MtR¹ ₃   (II) wherein Mt is a metal belonging to Group 13 of thePeriodic Table of the Elements, R¹, equal to or different from eachother, are halogen atoms, halogenated C₆-C₂₀ aryl or halogenated C₇-C₂₀alkylaryl groups; two R¹ groups can also form with the metal Mt onecondensed ring, and c) optionally a compound of formula KR^(f) ₃ whereinK is a nitrogen (N) or phosphorous (P) atom; R^(f), equal to ordifferent from each other, are linear or branched, saturated orunsaturated, C₁-C₃₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms,or two R^(f) can form one C₄-C₇ ring, optionally containing O, S, N, Por Si atoms, that can bear substituents.
 16. The catalyst systemaccording to claim 15 further comprising an alkylating agent.
 17. Thecatalyst system according to claim 15 wherein the organometalliccompound B) is chosen from the following formulae (III), (V), (IV),(VI), (VII), (IX), (VIII) or (X):

wherein Mt is a metal belonging to Group 13 of the Periodic Table of theElements (IUPAC); R¹, equal to or different from each other, are halogenatoms, halogenated C₆-C₂₀ aryl or halogenated C₇-C₂₀ alkylaryl groups;or two R¹ groups can form with the metal Mt one condensed ring; thesubstituents R⁵, R⁴ and R³ equal to or different from each other, arehydrogen atoms, halogen atoms, linear or branched, saturated orunsaturated C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms,or two or more adjacent substituents R³, R⁴ and R⁵ form one or moreC₄-C₇ rings, optionally containing O, S, N, P or Si; R² is a linear orbranched, saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀arylalkyl or C₇-C₂₀ alkylaryl group, optionally containing O, S, N, P,Si or halogen atoms or R² can join R⁵ to form a C₄-C₇ ring,

wherein B is a boron atom; the substituents R⁶, the same or differentfrom each other, are hydrogen atoms, halogen atoms, linear or branched,saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl orC₇-C₂₀ alkylaryl groups optionally containing O, S, N, P, Si or halogenatoms, or two or more adjacent substituents R⁶ form one or more C₄-C₇,optionally containing O, S, N, P or Si atoms rings that can bearsubstituents;

wherein the substituents R^(3′), R^(4′) and R^(5′), equal to ordifferent from each other, are hydrogen atoms, halogen atoms, linear orbranched, saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀arylalkyl or C₇-C₂₀ alkylaryl groups, optionally containing O, S, N, P,Si or halogen atoms, or two or more adjacent substituents R^(3′), R^(4′)and R^(5′) form one or more C₄-C₇ rings, optionally containing O, S, N,P or Si atoms, that can bear substituents; said rings can be aliphaticand optionally contain double bonds; with the proviso that said ringsare not aromatic; R^(2′) is a linear or branched, saturated orunsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀alkylaryl group, optionally containing O, S, N, P, Si or halogen atoms;or R^(2′) can join R^(5′) to form a C₄-C₇ ring;

wherein K is a nitrogen (N) or phosphorous (P) atom; R^(f) equal to ordifferent from each other, are linear or branched, saturated orunsaturated, C₁-C₃₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms,or two R^(f) can form one C₄-C₇ ring, optionally containing O, S, N, Por Si atoms, that can bear substituents,


18. The catalyst system according to claim 15 wherein the transitionmetal organometallic compound is a metallocene compounds belonging tothe following formula (XI):(Cp)(ZR⁷ _(m))_(n)(A)_(r)ML_(p)   (XI) wherein (ZR⁷ _(m))_(n) is adivalent group bridging Cp and A; Z being C, Si, Ge, N or P, and the R⁷groups, equal to or different from each other, being hydrogen or linearor branched, saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl,C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkyl groups or two R⁷ canform a aliphatic or aromatic C₄-C₇ ring; Cp is a substituted orunsubstituted cyclopentadienyl group, optionally condensed to one ormore substituted or unsubstituted, saturated, unsaturated or aromaticrings, containing from 4 to 6 carbon atoms, and optionally containing atleast one heteroatom; A is O, S, NR⁸, or PR⁸ wherein R⁸ is hydrogen, alinear or branched, saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkyl, or A hasthe same meaning of Cp; M is a transition metal belonging to group 4, 5or to the lanthanide or actinide groups of the Periodic Table of theElements; the substituents L, equal to or different from each other, aremonoanionic sigma ligands selected from the group consisting of hydrogenatoms, halogen atoms, R⁹, OR⁹, OCOR⁹, SR⁹, NR⁹ ₂ and PR⁹ ₂, wherein R⁹is a linear or branched, saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkyl group,optionally containing one or more Si or Ge atoms; m is 1 when Z is N orP, and it is 2 when Z is C, Si or Ge; n is an integer ranging from 0 to4; r is 0, 1 or 2; n is 0 when r is 0; p is an integer equal to theoxidation state of the metal M minus r+1.
 19. The catalyst systemaccording to claim 15 wherein the transition metal organometalliccompound is a late transition metal complex of formula (XII) or (XIII):L^(a)M^(a)X^(a)p^(a)   (XII)L^(a)M^(a)A^(a)   (XIII) wherein Ma is a metal belonging to Group 8, 9,10 or 11 of the Periodic Table of the Elements; L^(a) is a bidentate ortridentate ligand of formula (XIV):

wherein: Q is a C₁-C₅₀ bridging group linking E¹ and E², optionallycontaining at least one atom belonging to Groups 13-17 of the PeriodicTable; E¹ and E², equal to the same or different from each other, areelements belonging to Group 15 or 16 of the Periodic Table and arebonded to said metal M^(a); the substituents R^(a1), equal to ordifferent from each other, are selected from the group consisting ofhydrogen, linear or branched, saturated or unsaturated C₁-C₂₀ alkyl,C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkylradicals, optionally containing at least one atom belonging to groups13-17 of the Periodic Table of the Elements; or two R^(a1) substituentsattached to the same atom E¹ or E² form a saturated, unsaturated oraromatic C₄-C₇ ring, having from 4 to 20 carbon atoms; m^(a) and n^(a)are independently 0, 1 or 2, depending on the valence of E¹ and E², soto satisfy the valence number of E¹ and E²; q^(a) is the charge of thebidentate or tridentate ligand so that the oxidation state of M^(a)X^(a)_(p)X^(a′) _(s) or M^(a)A^(a) is satisfied, and the compound (XII) or(XIII) is overall neutral; X^(a), equal to or different from each other,are monoanionic sigma ligands selected from the group consisting ofhydrogen, halogen, R^(a), OR^(a), OSO₂CF₃, OCOR^(a), SR^(a), —NR^(a) ₂and PR^(a) ₂ groups, wherein the R^(a) substituents are linear orbranched, saturated or unsaturated, C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl,C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀ arylalkyl radicals, optionallycontaining one or more atoms belonging to groups 13-17 of the PeriodicTable of the Elements; or two X^(a) groups form a metallacycle ringcontaining from 3 to 20 carbon atoms; p^(a) is an integer ranging from 0to 3, so that the final compound (XII) or (XIII) is overall neutral; andA^(a) is a π-allyl or a π-benzyl group.
 20. A process for thepolymerization of at least one olefin comprising contacting at least oneolefin under polymerization conditions with a catalyst system,comprising the product obtained by contacting: (A) at least onetransition metal organometallic compound; and (B) an organometalliccompound obtained by contacting: a) a compound having the followingformula (I):

wherein R^(a) is a linear or branched, saturated or unsaturated, C₁-C₁₀alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀ alkylaryl group,optionally containing O, S, N, P, Si or halogen atoms; or R^(a) can joinR^(d) to form a C₄-C₇ ring; R^(b), R^(c) and R^(d), equal to ordifferent from each other, are hydrogen atoms, halogen atoms, linear orbranched, saturated or unsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀arylalkyl or C₇-C₂₀ alkylaryl groups, optionally containing O, S, N, P,Si or halogen atoms, or two or more adjacent substituents R^(b), R^(c),and R^(d) form one or more C₄-C₇ rings, optionally containing O, S, N, Por Si atoms, that can bear substituents; b) a Lewis acid of formula(II):MtR¹ ₃   (II) wherein Mt is a metal belonging to Group 13 of thePeriodic Table of the Elements; R¹, equal to or different from eachother, are halogen atoms, halogenated C₆-C₂₀ aryl or halogenated C₇-C₂₀alkylaryl groups: two R¹ groups can also form with the metal Mt onecondensed ring, and c) optionally a compound of formula KR^(f) ₃ whereinK is a nitrogen (N) or phosphorous (P) atom; R^(f), equal to ordifferent from each other, are linear or branched, saturated orunsaturated, C₁-C₃₀ alkyl, C₆-C₂₀ aryl, C₇-C₂₀ arylalkyl or C₇-C₂₀alkylaryl groups, optionally containing O, S, N, P, Si or halogen atoms,or two R^(f) can form one C₄-C₇ ring, optionally containing O, S, N, Por Si atoms, that can bear substituents.